The present disclosure relates to imaging displays. More in particular, it relates to color display materials and related methods and devices, such as methods and devices for displaying color images with ambient light sources.
As electronic imaging displays become more ubiquitous, there is an increased demand for low power consumption display technologies. In addition, there is a demand for display technologies which do not rely on an internal light source—displays which require only ambient light—allowing for easier visibility in high brightness conditions. An example of a display technology meeting both requirements is the E-Ink active matrix display. However, this technology is currently limited to black and white.
Provided herein are devices, and related arrays, methods and systems that in some embodiments, allow a variable reflectance element actuated through electrostatic means.
According to a first aspect, a pixel device is described. The pixel device comprises a fluidic structure, a plurality of ink particles, at least one transparent or translucent first electrode and at least one second electrode. In the pixel device, the plurality of ink particles comprise ink particles differing in electrical charge and/or mass contained within the fluidic structure. In the device, the element are configured so that a first electric field is generated when the first electrode and the second electrode are biased, causing the plurality of ink particles to selectively migrate toward the at least one first electrode according to the mass of the ink particles.
According to a second aspect a display device is described, that comprises an array of the pixel device herein described.
According to a third aspect, a method of ink particle stratification is described. The method comprises, providing a structure that contains at least one first electrode and at least one second electrode, configured to allow generation of a first electric field upon biasing of the at least one first electrode and the at least one second electrode. The method further comprises providing ink particles of identical charges but different masses; and biasing the structure; wherein the ink particles migrate toward the at least one first electrode.
According to a fourth aspect, a variable reflectance pixel device is described, the variable pixel device comprising: a substrate, a charged material, an insulating fluid, a conducting film, and an electrode. In the variable pixel device, the substrate has a top surface and a bottom surface, with at least one well, wherein the at least one well contains an opening at the top surface of the substrate. In the variable pixel device, the charged material is shaped to fit into, and contained within, the at least one well; and the insulating fluid is contained within the at least one well. In the variable pixel device, the conducting film is electrically insulated from the substrate, covers the top surface of the at least well; and the electrode contacts the bottom surface of the substrate.
According to a fifth aspect, a method of assembling a pixel array of a plurality of variable reflectance pixels is described. The method comprises: providing a substrate containing a plurality of differently shaped wells; and providing a block suspension containing at least one block of charged material of one or more shapes and an insulating fluid. The method further comprises selectively delivering the block suspension to the substrate, whereby the at least one block of charged material of one or more shapes become trapped in the plurality of differently shaped wells if the at least one pixel block of one or more shapes matches the shape of the plurality of differently shaped wells.
The devices, arrays, methods and systems herein described can be used in connection with electronic imaging display, e.g. liquid crystal display, or electrochromic display, laser technology and various additional applications identifiable by a skilled person upon reading of the present disclosure, wherein controllable positioning of particles is desirable.
The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more embodiments of the present disclosure and, together with the detailed description, serve to explain the principles and implementations of the disclosure.
Embodiments of the present disclosure are directed to devices, and methods to manufacture such devices, capable of providing analog color contrast and analog two-tone images, which utilize microfluidic stratified chromatography cells and variable reflectance pixels.
In the illustration of
In the illustration of
In the illustration of
An analog voltage (54) can be applied to a top electrode plate (53), attracting the ink particles to the top surface of the structure of
In an embodiment, in the structure of
In some embodiments, the top electrode plate (53) of the structure of
In some embodiments of the structure of
In one embodiment, by selecting the corresponding masses/shapes and charges of the various ink particles (52) (e.g. white ink, 1 ng; blue ink, 2 ng; red ink, 3 ng), a desired resulting color can be displayed in the translucent and/or transparent portion of the device of
In an embodiment, a chromatically separated column of ink particles (60) (white on top, blue in the middle, and red on the bottom) can be generated. By applying a second electric field (57, 58, 59) perpendicular to the original electrode configuration of the top and bottom electrode plates, ink particles of unwanted colors can be “wicked” away from the column of ink particles such that the ink particles of unwanted colors are moved underneath the opaque thin film. This is achieved with the placement of electrodes (first side electrode (58) and second side electrode (59)) such that the second electric field only accelerates the upper portion of the chromatically separated column of ink particles (60). This process allows one to control the exact color seen by the user.
In particular, in an embodiment, the second “wicking” electrical field can be used to accelerate the charged particles (52) at the top of the cell by translation (in the x-y plane). In this way, the charged particles (52) at the top are moved to the portion of the cell that is opaque. However, since flow in the cell is laminar and since the fluid is density matched, the displacement of particles (52) at the top of the cell will force the beads right below them to move up. If another color is desired then another pulse of the vertical field can be applied to displace the particles over thus create that flow of particles that can be controlled to move the desired particles on the displaying portion of the cell.
In one embodiment, the microfluidic stratified chromatographic cell (50) can be used to create pixels for a more controlled analog two-tone display. For example, white and black ink particles of various masses and volumes (e.g. white ink particles of mass 1 ng, white ink particles of mass 2 ng, black ink particles of mass 1 ng, and black ink particles of mass 2 ng) can be placed in the microfluidic structure. Assuming that the white ink particles and black ink particles are both positively charged, with the white ink particles being more positively charged than the black particles, the careful application of an actuation voltage on the top electrode can be used to create a spectrum of shades. For example, with the application of a small positive voltage, only the less-massive white ink particles will be attracted to the top surface of the microfluidic structure, resulting in a pixel that is whitish. The application of a larger positive voltage will allow the more massive white ink particles and the less massive black ink particles to overcome the retardation due to the gravitational force, resulting in a much “grayish” pixel. Various tonalities can be achieved by controlling charges, masses of the ink particles in view of the voltage applied.
Additional variables that can be modified to control the color that is displayed comprise shape and volume of the particles (that can be varied among as long as the volume to mass ratio of the particles in a same cell is substantially the same), and the amount of charges for each particle which can be increased or decreased to have a desired acceleration upon application of certain voltage.
In the illustration of
Attached to the substrate, below the bottom surface of the well, a bottom electrode (75) is attached in order to create an electric field with the transparent conducting film (74) in view of the presence of insulating fluid (73). In particular, in the illustration of
In the illustration of
As would be understood by those skilled in the art, in the illustration of
In the illustration of
The well depth is designed such that when the material (70) is at the bottom of the well (71), the material (70) is optically obscured by the opaque, insulating fluid. For example, with a white insulating fluid, with the material (70) at the bottom of the well (71), the top surface of the well (71) would appear white. However, with the pixel moved to the upper position against the transparent conducting film, the top surface would display the color of the material (70). Any other color can be used for the insulating fluid (73), according to the desired effect. For example, typically, a white or a gray (73) is desired for a “neutral” state.
In some embodiments, the outline (top view) of the shape of the well (71) can take a variety of forms, as shown in
In applications where visualization is desired, a pixel is provided by a cell comprising a plurality of wells (71) including a plurality of colored material (70) that is configured so that a desired color is displayed as a result of an applied voltage in the plurality of wells (71). In an embodiment, a cell includes a plurality of wells arranged in an array. A plurality of cells can also be arranged in an array used in connection with an application where a plurality of pixels is desired (e.g. LCD technology).
In some embodiments, a cell containing 3 different types of charged material in corresponding wells can be fabricated, as shown in
In an embodiment, the arrangement of
In an embodiment, a cell can contains wells of different shapes, in a configuration such as the one exemplified in
A cross sectional view of the display cell of
According to an embodiment of the present disclosure, a method of passively assembling a pixel array of variable reflectance pixels is described. A fabricated substrate with many wells is used. The wells can be of a fixed set and combination of shapes (e.g. circles, triangles, squares, etc) for which there are corresponding material blocks. Each material block can fit into any well of its type (i.e. corresponding shape), but only wells of its type. The material blocks are mixed with an insulating fluid to form a solution of suspended material blocks. This solution is then delivered to the substrate (or the substrate is submersed in it). If the blocks are small enough for Brownian motion to agitate them, they will randomly bounce off the surface of the substrate until they hit a well of their type, at which point they will become trapped. In some embodiments, a voltage may be applied to the substrate, and ultrasonic agitation to the insulating fluid, to aid in this alignment process.
According to some embodiments of the present disclosure, a method of selectively assembling a pixel array of variable reflectance pixels is described. If independent electrodes are fabricated on each well, or on groups of wells, then the process may be performed as for passively assembling the pixels, with the addition of selective application of voltage to specific wells or groups of wells. This step will preferentially draw in the suspended pixel blocks. In some embodiments, one could use a set of solutions, each containing one type of pixel block, to flow over the substrate, while electrically activating only the desired wells in the substrate, resulting in the selective filling of an array with pixels. This process would allow the sequential filling of all of the types of wells on the substrate quickly, with a low likelihood of incorrect pixels becoming trapped on the substrate. As a non-limiting example, consider a system with two types of pixels (“A” and “B”) and a substrate with corresponding wells. First, voltage is applied to only the “A” wells on the substrate, and a solution containing only type “A” pixel blocks is placed in contact with the substrate. The “A” type pixel wells are then rapidly filled, with minimal interaction between the floating pixel blocks and the “B” type wells.
If an electrically selective assembly works with a low enough error rate, so that only electrically activated pixel wells are filled, then it is possible to fill an array of identical wells with an array of identically shaped, but differently colored material as will be understood by a skilled person. This is particularly possible if the trapped charge on a block material is adequate to create a shielding potential from a well (e.g. by virtue of the Couloumbic shielding phenomenon). If this is the case, the electric field decays across a characteristic distance known as the Debye length. The charge for the shape that fills the well, will “shield” the other charged shapes from the charge on the bottom of the well. Therefore, the chances that these other shapes can be accelerated to the bottom of the well are minimized. As a consequence, a filled well, even with voltage applied to it, can appear charge neutral to a suspended pixel block, and thus energetically unfavorable.
According to an embodiment, a method of assembling a color display of variable resistance pixels is described. First, an array of 3 or more types, i.e. shapes, of wells is fabricated in a substrate. The backside of the substrate is patterned with an array of electrodes aligned to the cells. In particular, a display cell consists of three or more “wells”, each corresponding to a single color. By controlling which wells are filled, the color displayed by the cell can be determined. The array is then filled with charged material blocks using one the fluidic assembly techniques described in one of the embodiments herein. There are 3 pixel block types, each with a corresponding color (red/green/blue). Once filled, the array can be capped with an electrically insulating film on which there is an array of a transparent conducting film (e.g. ITO), also aligned to the cells.
In particular, the spacing between the ITO and the substrate determines the field intensity for a given voltage. A first order approximation of this relationship is E-field=V/d, where V is the applied voltage between the ITO and substrate, and d is the spacing between the ITO and the substrate. Fields on order 1 MV/m are expected to be used for pixel actuation.)
By using the electrical arrays to apply voltage to selective pixels, the reflectance of each pixel in the array can be controlled as will be understandable by a skilled person. By controlling all of the pixels in this fashion, images in color can be displayed as will be understandable by a skilled person.
The description set forth above is provided to give those of ordinary skill in the art a complete disclosure and description of how to make and use the embodiments of the assembly, components, devices, systems and methods of the disclosure, and are not intended to limit the scope of the disclosure. Although any methods and materials similar or equivalent to those described herein can be used in the practice for testing of the assembly, components, device(s) and methods herein disclosed, specific examples of appropriate materials and methods are described herein.
Modifications of the above-described modes for carrying out the device(s) and methods herein disclosed that are obvious to persons of skill in the art are intended to be within the scope of the following claims. All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the disclosure pertains. All references cited in this disclosure are incorporated by reference to the same extent as if each reference had been incorporated by reference in its entirety individually.
It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise The terms “multiple” and “plurality” includes two or more referents unless the content clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure pertains.
A number of embodiments of the device(s) and methods herein disclosed have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other embodiments are within the scope of the following claims.
The present application claims priority to U.S. Provisional Application No. 61/185,523, filed on Jun. 9, 2009, and U.S. Provisional Application No. 61/222,356, filed on Jul. 1, 2009, each incorporated herein by reference in their entirety.
The U.S. Government has certain rights in this invention pursuant to Grant No. HR0011-01-1-0054 awarded by DARPA and Grant No. DMR0520965 awarded by the National Science Foundation.
Number | Date | Country | |
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61185523 | Jun 2009 | US | |
61222356 | Jul 2009 | US |